dickson



NITED STATES PATENT OFFICE.

AROI-IIBALD A. DIOKSON, OF TORONTO, CANADA.

METHOD OF TREATING HYDROUS ROCK.

SPECIFICATION forming part of Letters Patent No. 620,894, dated March 14, 1899.

Application filed December 3,1897- Serial No- 660,677. (No specimensl T0 aZZ whom it may concern:

Be it known that I, ARCHIBALD ANDERSON DICKSON, a subject of the Queen of Great Britain, and a resident of the city of Toronto, in the county of York and Province of Ontario,- in the Dominion of Canada, have invented a certain new and useful Improved Method of Treating Hydrous Rock, of which the following is a specification.

This invention relates to the treatment of hydrous materials of a rocky character found in natural deposits or veins in the different forms of sulfate of limesuch as gypsum, (OaO,SO -]-2I-IO,) selenite, alabaster, and the likefor the purpose of rendering them capable of being readily hardened and polished, and whereby various useful and ornamental articles and materials may be prod uced,either plain or colored, to resemble different kinds of marble, chalcedony, onyx, or the like, the object being to perform such work and to produce such articles and materials in a manner more economically, conveniently, and efliciently than by the other methods known in the art.

In practice it has been found that one of the chief difficulties has been that during the process of dehydration the native material has been found to curl and twist to such an extent as to destroy the form or. equality of shape of the article or block under treatment. Another fatal objection to all of the old methods with which I am acquainted is that in the majority of cases cracking or slaking of the material occurs both during the dehydrating and cooling process.

I will now describe my new method or process in such detail as will enable those skilled in the art to put the same into practice and more particularly point out the novelty in the claim.

In mining the native material (which for clearness of description I will confine to gypsum rock) I use channeling or sawing machines in preference to breaking out or blasting, as the rock is thus in no danger of becoming fractured, shattered, or separated in its pores. The blocks or pieces are now sawed, turned, or otherwise worked into the desired shapes, and then preferably put into clamps or other holding devices of such character that a support or slight pressure will be had at the necessary points. These clamps or holders may include in their grasp either single articles or pieces or a number of such as may suit the circumstances, their use, how'- ever, being-specially valuable when used in connection with pieces of large dimensions.

The next step is that of dehydration-that is to say, I drive off the desired or necessary proportion or amount of the inherent moisture by subjecting the articles or piecest-o the of the material is thus effected, (or in using a large plant I may find it convenient'to move the dehydrated material to one or more cooler chambers, thus keeping up a constant operation with a large quantity of gypsum.) The desired degree of coolness having been thus,

effected, I prepare a bath containing a solution (preferably of the same temperature as is now possessed by the gypsum) of ammonium alum, A1 ,3SO (NH )2,SO ,24=H O, and immerse the articles (with their clamps still in place when such are used) therein and let them remain until the pores are completely filled with this hardening solution, or he quent hasty dippings may be employed in certain cases to some advantage, as kn own in the art. The use of ammonium alum in the bath is the essential feature of my process, as I find that this chemical from the peculiar penetrating action of the constituent ammonia acts both as a mordant and a hardening element, and I am consequently able to dispense with extra liquids, acids, and salts, and thus economize both labor and first cost of materials. Upon their removal from the bath I allow the slabs or other articles to drain and dry, preferably in the open'air or in a the bath, according to the appearance desired for thearticle, and I may sometimes employ those natural materials which are the closer affinities of the pure ammonium alumsuch as chrome-alum, iron-alum, and the like-in addition to the ammonium alum, when they produce the desired colors. The clamps or holders when used are now removed and the blocks, slabs, or ornamental pieces can be polished by any known or suitable means or methods.

I have found by practical experiment that the above process produces a finished article of superior hardness and free from crack or blemish, and the chemicals employed are such as will not be objectionable or dangerous to' the workmen employed.

I do not claim nor is it necessary to describe any particular form or arrangement of apparatus, as any intelligent person may eas= ily construct and arrange a plant suitable for carrying out my present improved process.

What I claim, and desire to secure by Letters Patent, is-

The process of treating hydrous gypsum rock to enable it to be hardened, which consists, essentially, in first dehydrating the rock by the action of heat; second, cooling it gradually; third, subjecting it to the action of a combined mordant and hardening material by immersing it in a single solution of ammo nium alum, A1 ,3SO (NII )2,SO ,24CII O until the mass has been thoroughly impregnated therewith and the pores filled, and finally drying it, substantially as set forth.

ARCHIBALD A. DICKSON.

Witnesses:

RoBT. A. KELLoNn, E. J. GHEcKLnY. 

